Accelerator Report: Run 3 operations counting down to LS3

By Bettina Mikulec, Leader of the Operations Group (BE-OP)

With accelerator operations for 2025 having ended on 8 December and the Linac4 source restarting already on 5 January, this year’s transition felt particularly short. While there was formally a year-end technical stop (YETS), accelerator activity resumed almost immediately, leaving little sense of a real pause. Nevertheless, many teams made effective use of the short stop, carrying out essential maintenance and selected improvement activities, as outlined in the previous report.

As every year, the CERN accelerator complex is restarting in a carefully sequenced manner, from the Linac4 source through the accelerator complex all the way up to the LHC, together with the attached experimental facilities. Once responsibility is handed over from shutdown coordination to the operations teams, each accelerator follows its established restart sequence: DSO (Departmental Safety Officer) tests to verify the integrity of the safety systems, equipment and control checks, machine checkout, and finally beam commissioning to prepare the beams required for the downstream machines and users.

As can be seen in figure 1, Linac4 and the PS Booster have already completed their standalone beam commissioning successfully and have handed over the baton to the PS. The East Area and the SPS are following closely behind. According to the current schedule, the 2026 physics programme will begin on 5 February with n_TOF, followed by the East Area on 11 February.